Apparatus for preparing and stacking metal pallets

ABSTRACT

Apparatus for cleaning, oiling and stacking sheet metal pallets. The apparatus includes a conveyor operable to carry pallets in succession along a path past a scraper for removing material therefrom and past a lubricant applicator for applying a coating of lubricant to its top. A horizontally and vertically shiftable electromagnetic head is mounted at the downstream end of the conveyor path for magnetically gripping a cleaned and oiled pallet, and lowering it gently and quietly onto an underlying pallet support, or stack of previously deposited pallets. The electromagnetic head is mounted on the rod end of an upright ram for raising and lowering therewith. Further, the head is mounted for limited vertical shifting relative to the rod between an extended position relative to the shaft, and a retracted position relative to the shaft, and is yieldably biased by a spring toward its extended position. When extension of the ram lowers a pallet onto the underlying stack support, further extension of the ram causes the rod to move downwardly while the head remains stationary. A sensing switch on the head is operable to sense such movement of the shaft relative to the head and is operable to release the magnetic hold of the head and cause it to raise to a position ready to grab another pallet.

United States Patent [191 Schmitt [4 1 Sept.2, 1975 APPARATUS FOR PREPARlNG AND STACKING METAL PALLETS [75] Inventor: Robert A. Schmitt, Vancouver,

Wash.

[73] Assignee: Columbia Machine, Inc.,

Vancouver, Wash.

[22] Filed: Sept. 11, 1974 [21] Appl. No.: 505,070

[52] US. Cl. 15/93; 15/77; 118/236; 214/6 FS [51] Int. Cl. B23D 79/02 [58] Field of Search 15/77, 93, 102; 118/236; 214/6 FS; 271/D1G. 3

[56] References Cited UNITED STATES PATENTS 2,565,927 8/1951 Morgan 214/6 FS X 3,292,194 12/1966 Randall 15/77 Primary Examiner-Edward L. Roberts Altorney, Agent, or Firml(olisch, Hartwell, Dickinson & Stuart [57] ABSTRACT Apparatus for cleaning, oiling and stacking sheet metal pallets. The apparatus includes a conveyor operable to carry pallets in succession along a path past a scraper for removing material therefrom and past a lubricant applicator for applying a coating of lubricant to its top. A horizontally and vertically shiftable electromagnetic head is mounted at the downstream end of the conveyor path for magnetically gripping a cleaned and oiled pallet, and lowering it gently and quietly onto an underlying pallet support, or stack of previously deposited pallets. The electromagnetic head is mounted on the rod end of an upright ram for raising and lowering therewith. Further, the head is mounted for limited vertical shifting relative to the rod between an extended position relative to the shaft, and a retracted position relative to the shaft, and is yieldably biased by a spring toward its extended position. When extension of the ram lowers a pallet onto the underlying stack support, further extension of the ram causes the rod to move downwardly while the head remains stationary. A sensing switch on the head is operable to sense such movement of the shaft relative to the head and is operable to release the magnetic hold of the head and cause it to raise to a position ready to grab another pallet.

8 Claims, 10 Drawing Figures PATENTED SEP 2 75 SHEET 2 [IF 3 PATENTEDSEP 21975 SHEET 3 OF 3 QNN APPARATUS FOR PREPARING ANlD STACKING METAL PALLETS BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to apparatus for preparing sheet metal pallets for use and thereafter gently and quietly depositing them on a stack.

In the past, various devices have been designed for cleaning and preparing sheet metal pallets for reuse. Such prior devices. however, have usually been quite noisy, and rather hard on the pallets, in that they have merely relied on the force of gravity to deposit them on stacks after they have been prepared. Generally, the pallets have been merely discharged from the downstream end of preparing apparatus, and allowed to drop onto an underlying stack support. This is not only hard on the pallets, but also produces considerable noise.

With the advent of stricter governmental regulations regarding levels of noise in work areas, it has become necessary for operators to perform such operations with a minimum amount of noise.

A general object of the present invention is to provide novel apparatus for preparing sheet metal pallets, which is operable to handle such pallets in a quiet and efficient manner.

More specifically, an object of the invention is to provide such apparatus which includes a vertically shiftable magnetic head operable to magnetically grip a pallet after preparation and thereafter to produce controlled lowering of the pallet in a gentle and quiet manner onto an underlying stack, thus to reduce noise.

Another object of the present invention is to provide such apparatus in which a sensing device is operable to sense when a pallet has been lowered into position on an underlying stack support, release the magnetic grip of the magnet on the pallet. and return the head to a raised position to await a successive pallet for lowering.

DRAWINGS These and other objects and advantages will become more fully apparent as the following description is read in conjunction with the drawings, wherein:

FIG. I is a top plan view of apparatus constructed according to an embodiment of the invention with central portions thereof broken away to reduce its length for illustration;

FIG. 2 is a side elevation view of the apparatus illustrated in FIG. 1;

FIG. 3 is an enlarged, simplified top plan view of opposite end portions of pallet moving mechanism in the apparatus;

FIG. 4 is a longitudinal section of the apparatus illustrated in FIG. 4 taken generally along the line 44 of FIG. 3:

FIG. 5 is an end elevation view of pallet feed mechanism in the apparatus taken generally along the line 55 in FIG. 2;

FIG. 6 is an enlarged view of opposing portions of the apparatus indicated by lines 6-6 in FIG. 5;

FIG. 7 is an enlarged view of pallet scraping mechanism in the apparatus taken generally along the line 7-7 in FIG. 2;

FIG. 8 is a view of magnetic pallet handling mechanism taken generally along the line 88 in FIG. 4;

FIG. 9 is an enlarged cross-sectional view taken generally along the line 99 in FIG. 8; and

DETAIL DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Referring to the drawings, and first more specifically to FIGS. 1 and 2, at 10 is indicated generally apparatus constructed according to an embodiment of the invention. The specific apparatus described, as will be explained in greater detail below, is operable to receive sheet metal pallets which have been used to support concrete blocks during molding and thus have bits of concrete adhered thereto, scrape and lubricate the surfaces of the pallets and then set them gently and quietly in succession on a stack support. The apparatus includes a main frame 12 which includes a pair of parallel, horizontally disposed, laterally spaced, elongate channels 14, 16 which are supported adjacent opposite sets of their ends by upright posts 20. Posts 20 may be adjustable in height to accommodate variations in the contour of an underlying floor surface and thus support channels 14, 16 substantially horizontally a preselected distance above the floor.

Referring to FIGS. 4 and 8, secured to the inwardly facing surfaces of channels l4, l6 and extending substantially horizontally and longitudinally thereof, are a pair of elongate pallet support strips 22, 24. Strips 22, 24 are laterally spaced apart a distance whereby they may support opposite end margins of a plurality of rectangular sheet metal pallets disposed edge-to-edge in a row as illustrated generally at 2811-28e in FIGS. 3, 4 and 8.

Referring to FIGS. 3 and 4, a pair of elongate, substantially horizontal confining strips 32, 34 are secured in positions overlying support strips 22, 24, respectively, with the vertical spacing between the confining and support strips being just slightly greater than the thickness of a pallet 28. This permits sliding of pallets therebetween while preventing contiguous edges of adjacent pallets from riding up and over each other. As is seen in FIGS. 3 and 4, the upstream, or right, set of ends of the support strips and confining strips are adjacent each other, while at the downstream end of the apparatus the support strips extend further downstream in the apparatus than the confining strips.

At the upstream, or infeed, end of the apparatus (at the right ends of FIGS. 1 and 2) is illustrated apparatus for feeding pallets in succession to a region adjacent the upstream, or infeed, ends of the support and confining strips. Such infeed apparatus includes a pair of laterally spaced, power-driven conveyor chains 38, 40 having substantially horizontal upper reaches disposed at elevations below the elevation of support strips 22, 24 and extending normally outwardly of the path for pallets provided by the support strips. As is best seen in FIGS. 1 and 5, chains 38, 40 are operable to carry a pallet 28 into position adjacent, but below, the infeed set of ends of the support and confining strips.

An elevator, indicated generally at 42, is operable to raise pallets carried to such region from the upper reaches of chains 38, 40 to a position in line with the upstream ends of the support and confining strips.

Referring to FIG. 2, elevator 42 includes a pair of guide sleeves 44, 46 mounted to guided vertical shifting on upright rods 48, 50. An elongate, substantially horizontal bar 52 is secured adjacent its opposite ends to the upper ends of guide sleeves 44, 46 and thereby interconnects the two. The rod end of an upright ram 54 is operatively connected to bar 52 whereby extension of the ram raises guide sleeves 44, 46 and retraction of the ram lowers them.

Referring to FIG. 5, secured to, and cantilevered outwardly from guide sleeves 44, 46 intermediate chains 38, 40 is a pallet engaging frame 58. When ram 54 is retracted, frame 58 is in its lowered position as illustrated in FIG. below the upper reaches of chains 38, 40. On extension of ram 54 frame 58 raises between chains 38, to engage the underside of a pallet 28 resting thereon and raises it to the level of the infeed set of ends of the confining and support strips as illustrated in FIG. 4.

Referring to FIGS. 4, 5 and 6, aligned with support strips 22, 24 are a pair of oppositely disposed pallet receivers 62, 64. As is best seen in FIG. 6, receivers 62, 64 are substantially mirror images of each other and thus only one will be described in detail. Referring to receiver 64, it includes a support member 66 pivotally mounted on a shaft 68 secured on frame 12. The pallet receiver also includes an elongate, substantially horizontal upper plate 70 extending substantially horizontally and in longitudinal alignment with support strip 24. An elongate, inclined lower plate 72 secured below plate 70, connects with the inwardly facing edge of plate 70 and inclines outwardly therefrom on progressing downwardly in the apparatus. A compression spring 74 interposed between support member 66 and a channel in the main frame yieldably urges the pallet receiver inwardly of the frame, away from the channel. An elongate bolt 76 acts as a stop member to limit rotation of member 66 under the urging of spring 74 to the position illustrated in FIG. 6.

As a pallet 28 is raised from chains 38, 40 by frame 58, its opposite ends engage lower plate 72 of the pallet receivers and force them to move apart against the biasing force of springs 74. The pallet receivers thus rock outwardly to positions illustrated in dot-dashed outline to permit raising of the pallet therepast to a position above the pallet receivers. Once the pallet is moved thcrcabove the pallet receivers swing back in and under opposite end margins of the pallet, to support the same at the elevation of support strips 22, 24 when the pallet engaging frame 58 is lowered.

Referring again to FIGS. 1, 2 and 8, mounted on and supported above the upstream set of ends of channels 14, 16 of the main frame are a pair of laterally spaced,

elongate, substantially horizontally disposed channels 82, 84. A similar pair of channels 86, 88 are disposed adjacent the downstream end of the apparatus. Channels 82, 84, 86, 88 are disposed with the webs thereof substantially vertical, and the flanges thereof projecting horizontally inwardly toward the longitudinal center line of the apparatus.

An elongate carriage frame, indicated generally at 94, is supported in channels 82, 84, 86, 88 for reciprocal movement in an upstream and downstream direction (to the right and left in FIGS. l4) relative to the main frame.

Referring to FIGS. 3 and 4, where carriage frame 94 is illustrated with support channels 82, 84, 86, 88 removed, the carriage frame includes a pair of elongate. substantially horizontal, laterally spaced channels 96, 98. Rollers, such as those indicated generally at in FIG. 8 journaled on channels 96, 98 support the same for rolling movement in support channels 82, 84, 86, 88 of the main frame.

An elongate, extensible-contractible ram 104 (see FIGS. 1, 3 and 4) is connected at one of its ends to the upstream end of main frame 12 and at its opposite end to a crossbar 106 on the carriage frame. Contraction of the ram places the carriage frame in the position illustrated in FIGS. 1, 2, 3 and 4, and extension of the ram moves the carriage frame in a downstream direction therealong, to the left in FIGS. l4.

Referring to FIGS. 3 and 4, secured to the upstream ends of channels 96, 98 are a pair of similarly shaped upright plates 108, 110. An elongate plate 112 extends between, and is secured adjacent its opposite ends to plates 108, 110. An elongate shaft 114 also extends between and is secured adjacent its opposite ends to plates 108, 110. Shaft 114 is spaced in an upstream direction from and at a lower elevation than plate 112.

A pair of pallet moving dogs 118, having the configuration illustrated in FIG. 4, are journaled adjacent their rearmost ends on shaft 114 in laterally spaced relation adjacent plates 108, 110, respectively. Since the majority of the weight of dogs 118, 120 is on the downstream side of shaft 114, their tendency is to rotate in a counterclockwise direction as illustrated in FIG. 4. Each has a projection, such as that indicated generally at 118a in FIG. 4, which engages plate 112 to prevent the dog from turning in a counterclockwise direction beyond the position illustrated in FIG. 4. The dog, however, is permitted rotation in the opposite direction. A pallet support lip, such as that illustrated at 118/) in FIG. 4 projects horizontally outwardly and in a downstream direction at the lower margin of each dog.

Each dog has a pallet hold-down member 122, 124, respectively, journaled thereon above its pallet support lip.

Pallet moving dogs I18, 120 and their respective hold-down members 122, 124 are adapted to grip the upstream edge ofa pallet, as illustrated in FIG. 4, as the carriage frame is shifted in a downstream direction to shove the pallet in a downstream direction toward the space between support strips 22, 24 and their overlying confining strips 32, 34. Such pushing of a pallet 28 from pallet receivers 62, 64 causes the pallet to engage a contiguous upstream end of pallet 28a previously shoved into the row of pallets on strips 22, 24, as illustrated in FIGS. 3 and 4, thus to shove the entire row in a downstream direction along a path between the support strips and confining strips. The positioning of the support and confining strips assures that contiguous edges of adjacent pallets will not ride up and over each other when a force is exerted thereagainst by actuation of the carriage frame to shove the row of pallets along the path.

A pallet scraper indicated generally at in FIGS. 2 and 7 is operable to scrape unwanted material, such as previously deposited bits of concrete, from the top surface of pallets passed therethrough. The scraper includes a plurality of contiguous scraper bits, or teeth. I32 secured in an elongate bar 134 overlying the path along which a pallet 28 is carried. A plurality of wheels I36 mounted on a shaft 138 are operable to hold a pallet tightly against the downwardly facing scraping surfaces of bits 132 to provide a positive scraping action as the pallets are passed thereunder.

Referring again to FIGS. I and 2, spaced downstream from scraper 130 is pallet lubricating mechanism indicated generally at 140. The lubrieator illustrated in eludes an elongate roller 142 dependently supported on a pair of arms 144 for bearing against the upper surfaces of pallets passed thereunder. A spray bar indicated generally at 146 is operable to deposit a film of oil on the roller which then is transferred to the upper surfaces of the scraped pallets.

Positioned downstream from the downstream end of frame 12 is a pallet receiving support 150 adapted to have cleaned and oiled pallets stacked thereon after passing through the apparatus. Support 150 includes a support table 152 on which a stack of pallets, such as that indicated at 154, may be placed and means for lowering the table incrementally as additional pallets are stacked thereon, thus to maintain the top of the stack generally at a preselected elevation relative to the frame.

Indicated generally at 160 adjacent the downstream end of the apparatus in FIGS. I4 and 8 and mounted on the downstream end of carriage frame 94 is pallet stacking mechanism operable to engage a pallet at the downstream end of support strips 22, 24, shift it horizontally to a position over table 152, lower it gently and quietly onto the underlying support table or stack, release the pallet and then return to operate upon a suceessive pallet at the downstream end of the support strips.

Describing the pallet stacking mechanism in detail, it includes an upright ram 164 mounted on a plate 166 extending between and secured adjacent its opposite ends to channels 96, 98 of the carriage frame. The rod 16411 of the ram is directed downwardly below plate 166.

Operatively connected to the lower end of rod 164a is an electromagnetic operating head 170. The magnetic head is connected to the lower end of rod 164::

in such a manner that it may move vertically with the rod and is permitted a degree of vertical shifting relative to the rod.

Describing the connection between rod 164a and head 170, a cylindrical collar 172 is secured to the top of and projects upwardly from a central region of head I70, surrounding a lower end portion of rod 164a. Collar 172 rests loosely on a collar 174 secured to rod 164a a distance spaced above the lower end of the rod. The lower end of rod 1640 also is spaced a distance above the upper surface of heat 170 permitting the head to move upwardly relative to the rod. A compression spring 178 is interposed between collar 174 and the upper surface of head 170 to yieldably bias the operating head to what is referred to herein as the ex tended position for the head relative to the rod as illustrated in FIG. 9. A retracted position for the head, shifted upwardly on rod 1640 is illustrated in FIG. 10.

Referring to FIG. 9, at 180 is indicated generally a pressure fluid supply connected to opposite ends of ram 164 through conduits 182, 184 for supplying fluid to and exhausting fluid from opposite ends of the ram for extending or retracting the same. A multiple position valve 186 is interposed in conduits 182, 184. When placed in one position valve 186 supplies pressure fluid to the lower end of ram 164 to retract rod 164a and raise head 170, in another position the valve supplies pressure fluid to the upper. end of the ram to produce extension of rod 164a and lowering of head 170, and in a third position the valve inhibits flow of pressure fluid to or return of pressure fluid from 164 to maintain the rod and operating head in a selected position.

Mounted on operating head for movement therewith is a limit switch 190 having a vertically swingable operating arm 190a. An annular disc 192 secured to rod 164a is positioned to be out of engagement with, and thus in a nonactuating position relative to arm 190a when the operating head is in its' extended position relative to rod 164a as seen in FIG. 9. On shifting of operating head 170 vertically relative to rod 164a, as illustrated in FIG. 10, arm 190a and disc 192 come into engagement with each other producing vertical swinging of arm 190a and actuation of the switch. Switch 190 is connected through a conductor 194 to a control circuit 196. Another limit switch 200 having an operating arm 200a is secured to cross plate 166. Its arm 200a is so positioned that it is engaged by the top of switch 190 when rod 164a of the ram is retracted to a selected position with operating head 170 spaced above the path of pallets 28, as seen in FIG. 8. A conductor 202 Operatively connects switch 200 to control circuit 196.

Each of switches 190, 200 is operable on actuation of its operating arm to produce a signal which is carried by its corresponding conductor to control circuit 196. Control circuit 196 is so constructed and Operatively connected to valve 186 that it is operable to produce shifting of valve 186 between various positions in accordance with signals received from switches 190, 200, respectively. Explaining further, on extension of ram 164, should operating head 170 come into contact with a stationary object, such as an underlying pallet or stack support, the operating head stops while rod 164:: and disc 192 continue downwardly. This downward movement causes disc 192 to engage arm 190a producing a signal through conductor 194 to the control circuit. Such signal causes valve 186 to shift to another position to produce retraction of the ram and associated raising of operating head 170. As the ram is retracted, and operating head 170 and switch 190 are raised, the top of switch 190 eventually will come into contact with actuating arm 200a of switch 200, at which time it produces a signal through conductor 202 to circuit 196. Such signal produces actuation of the circuit to shift valve 186 to a neutral position in which fluid is neither supplied to nor exhausted from ram 164 thus to hold the rod in a retracted position. Other control circuitry and valve actuating mechanism (not shown) connected to valve 186 is operable to shift valve 186 to a position in which fluid under pressure is supplied to and exhausted from the ram to initiate and produce extensionof the ram.

Mounted laterally to opposite sides of ram 164 on support plate 166 are a pair of upright guide sleeves 210. Elongate rods 212 extending vertically through sleeves 210 are secured at their lower set of ends to operating head 170 and slide vertically in sleeves 210 to guide vertical movement of the operating head on extension and retraction of ram 164.

An electrical source 214 is connected through control circuit 196 and conductors 216, 218 to operating head 170. When it is desired to grab a pallet 28 by the magnetic force of head 170 an electrical current is supplied to the operating head through conductors 216, 218.

A carriage position sensor, indicated schematically at 220 in FIG. 9, is connected to control circuit 196 by a conductor 222. Sensor 220 is operable to produce signals indicating to circuit 196 whether the carriage frame is in its retracted or extended position.

The construction of control circuit 196 is such that when sensor 220 indicates that the carriage frame is in its horizontally retracted position and an electrical current is supplied to the operating head from source 214, the operating head may be lowered against a pallet 28 thereunder to magnetically grab, or grip, the pallet. Further extension of rod 164a brings disc 192 into engagement with arm 190:: of the switch to produce a signal to control circuit 196 actuating valve 186 to halt extension of the ram, with current continuing to be supplied to head 170. If a signal from sensor 220 indicates to control circuit 196 that the carriage frame is extended, and thus the pallet stacking mechanism is extended to a position over table 152, when operating head 170 and a pallet held thereby is lowered against the top of an underlying stack or table 152, and disc 192 subsequently is lowered against the actuating arm of switch 190, the control circuit breaks the contact between source 214 and head 170, thus to release the magnetic grip of the head on the pallet. This permits raising of the head on retraction of the ram while leaving the pallet on the underlying table or stack.

Describing now the operation of the device, and referring first to FIGS. 1 and 5, rectangular sheet metal pallets, such as those indicated at 28 are carried by conveyor chains 38, 40 into a position overlying pallet engaging frame 58. Raising of frame 58 by operation of ram 54 (see FIG. 2) raises frame 58 under a pallet 28, to lift it from chains 38, 40 and move it upwardly between pallet receivers 62, 64 (see FIG. 6). As the frame moves the pallet between receivers 62, 64 they are urged to move apart to allow passage of the pallet therebetween, after which they swing back, in and under opposite edge margins of the pallet, as shown in solid outline in FIG. 6, thus to support the pallet at the elevation of a path along which the pallet is to be moved through the apparatus. Frame 58 then is lowered again by retraction of ram 54, below the elevation of chains 38, 40, to be in position to receive and raise the next successive pallet conveyed thereto by the chains.

Pallet 28 resting on the tops of receivers 62, 64 thus is in position to be engaged by dogs 118, 120 on carriage frame 94. Extension of ram 104 from the position illustrated in FIGS. 1, 3 and 4, brings dogs 118, 120 into engaging relationship with the rearwardly facing edge of pallet 120 on the pallet receivers 62, 64 and forces it in a downstream direction against the trailing edge of a pallet 28:! (see FIGS. 3 and 4) previously forced into the supporting spaces between support and confining strips 22, 24, 32, 34 on the main frame. A row of pallets previously placed into the apparatus are illustrated at 28a 280 in FIGS. 3 and 4.

As pallet 28 is shoved by movement of the carriage frame into the path for pallets between the support and confining strips, previously deposited pallets are shifted along the path under scraper bits 132 to scrape residual material from the top surfaces thereof, and under lubricant applicator 140 where a film of oil is applied to the tops of the pallets.

Referring to FIGS. 3 and 4 it will be seen that the dis- 6 tance between pallet moving dogs 118, 120 and head 170 is substantially equal to a positive odd integer multiplied by one half the length ofa pallet 28 as measured longitudinally of the apparatus. With such spacing between dogs 118, and head 170, when the dogs initially engage the rear end of a pallet to shove it along support strips 22, 24 head 170 is positioned substantially centrally over a pallet at the downstream ends of the apparatus.

Referring to FIG. 8, ram 164 in its nonoperating position is retracted with operating head 170 raised above the level of the path for pallets 28, as seen in FIG. 8. Prior to extension of ram 104, valve 186 is shifted to such position that pressure fluid is supplied through conduit 182 and exhausted from conduit 184 to produce extension of the ram, thus lowering head 170 against underlying pallet 286, as illustrated in FIG. 4. Concurrently, control circuit 196 is actuated to connect electrical source 214 and the operating head to produce an electromagnetic attraction, whereby when the head is lowered against an underlying pallet it grips the pallet magnetically.

After operating head 170 has been lowered against and magnetically grabbed pallet 28s, extension of ram 104 to shove the row of pallets in a downstream direction also causes the magnetic head to shift in a downstream direction to a position overlying pallet receiving support and a stack of pallets previously deposited thereon, as indicated at 154. This extended position for the operating head is illustrated in dot-dashed outline in FIGS. 3 and 4 and in solid outline in FIG. 9. After ram 104 has been extended to place head over stack 154, valve 186 is shifted again to a position to extend ram 164 to produce controlled lowering of operating head 170 and pallet 28e held thereby against the top of stack 154. The pallet thus is lowered gently and quietly onto the top of the stack.

When the pallet comes to rest on the top of the underlying stack downward movement of the operating head and switch 190 ceases. Since rod 164 continues to extend disc 192 will come into contact with operating arm 1900 of switch 190 (see FIG. 10) thus to produce a signal at control circuit 196 which will shift valve 186 to its ram retracting position and simultaneously, through control circuit 196, breaks the connection between electrical source 214 and operating head 170 to release the magnetic gripping of the pallet by the head. The head thus is able to retract from the stack leaving pallet 28e thereon. As the ram retracts to its fully raised position, as illustrated in FIG. 8, switch arm 200:! is contacted by the top of switch 190 to produce shifting of valve 186 to its neutral position which stops retraction of the ram.

Thereafter ram 104 is again retracted to place the carriage frame in its position ready to receive a successive pallet for operation.

While a preferred embodiment of the invention has been described herein, it should be apparent to those skilled in the art that variations and modifications are possible without departing from the spirit of the inven tion.

It is claimed and desired to secure by letters patent:

1. Apparatus for preparing the surfaces of sheet metal pallets for use and depositing them quietly on a stack comprising a conveyor for carrying a plurality of pallets in succession along a path,

means intermediate the ends of said path for cleaning a surface expanse of a pallet as it is carried by the conveyor along said path,

pallet support means adjacent and spaced at an clevation below the downstream end of the conveyor, and

pallet stacking means including a vertically shiftable electromagnetic head adjacent the downstream end of said conveyor, powered shifting means operatively connected to said head for shifting the same between a raised position above said downstream end of the conveyor for magnetically attaching to the upper surface of a pallet carried to the downstream end of the conveyor and a lowered position spaced below said raised position for depositing a pallet carried thereby onto said pallet support, and control means for sensing when a pallet has been deposited on said stack support and operable to release said magnetic attachment to deposit the pallet on the stack support.

2. The apparatus of claim 1, wherein said pallet support is spaced horizontally from the downstream end of the conveyor, and which further comprises means mounting said head for horizontal shifting between a pickup station adjacent the downstream end of said conveyor and a depositing station overlying said pallet support, and second powered shifting means operatively connected to said head for shifting the same between said pickup station and said depositing station.

3. The apparatus of claim 2, which further comprises a main frame, an elongate carriage frame extending generally in the direction of said path mounted for reciprocal movement on said main frame along said path, said head is mounted on said carriage frame adjacent the downstream end thereof, pallet engaging means is connected to said carriage frame adjacent its upstream end for engaging a pallet and carrying it along Said path on movement of the carriage frame along said path, and said second powered means is operatively connected to said carriage for shifting the same along said path.

4. The apparatus of claim 1, wherein said shifting means comprises a power actuated vertically shiftablc member, and which further comprises means mounting said head on said member for limited vertical shifting relative to said member between an extended position at the lower limit of shifting relative to said member and a retracted position shifted upwardly on said member from said extended position, and biasing means operatively interposed between said member and head yieldably urging the head toward its extended position.

5. The apparatus of claim 4, wherein said shifting means comprises an extensible-contractible ram disposed with its rod directed downwardly, said means mounting the head thereon comprises a connector member secured to said head and mounted on said rod for movement therewith and for vertical sliding movement relative thereto, means limiting shifting of said member between said extended and retracted positions relative to said shaft, and said biasing means comprises a compression spring interposed between said rod and said head.

6. The apparatus of claim 4, wherein said control means comprises means operable to sense shifting of said head between its extended and retracted positions and to produce release of said magnetic attachment on shifting of the head to its retracted position.

7. The apparatus of claim 6, wherein said sensing means comprises a switch element and a switch actuating element, withone of said elements being mounted on said head for movement therewith and the other of said elements being mounted on said vertically shift able member of said shifting means, with said elements being so positioned that they are spaced from each other when said head is in its extended position, and the switching element and actuating element are in switch operating positions when said head is retracted.

8. The apparatus of claim 1, which further comprises a main frame, said conveyor includes an elongate substantially horizontal carriage frame mounted for reciprocal movement on the main frame paralleling said path, drive means for producing reciprocal movement of the carriage frame a distance substantially equal to the dimension of a pallet measured in the direction of said path, and means adjacent the upstream end of the carriage for engaging a pallet when the carriage is retracted to an upstream position and for carrying such pallet therewith on movement of the carriage in the downstream direction, and said head is mounted on said carriage and spaced from said pallet engaging means a distance which is substantially equal to a positive odd integer multiplied by one-half of said dimen- 

1. Apparatus for preparing the surfaces of sheet metal pallets for use and depositing them quietly on a stack comprising a conveyor for carrying a plurality of pallets in succession along a path, means intermediate the ends of said path for cleaning a surface expanse of a pallet as it is carried by the conveyor along said path, pallet support means adjacent and spaced at an elevation below the downstream end of the conveyor, and pallet stacking means including a vertically shiftable electromagnetic head adjacent the downstream end of said conveyor, powered shifting means operatively connected to said head for shifting the same between a raised position above said downstream end of the conveyor for magnetically attaching to the upper surface of a pallet carried to the downstream end of the conveyor and a lowered position spaced below said raised position for depositing a pallet carried thereby onto said pallet support, and control means for sensing when a pallet has been deposited on said stack support and operable to release said magnetic attachment to deposit the pallet on the stack support.
 2. The apparatus of claim 1, wherein said pallet support is spaced horizontally from the downstream end of the conveyor, and which further comprises means mounting said head for horizontal shifting between a pickup station adjacent the downstream end of said conveyor and a depositing station overlying said pallet support, and second powered shifting means operatively connected to said head for shifting the same between said pickup station and said depositing station.
 3. The apparatus of claim 2, which further comprises a main frame, an elongate carriage frame extending generally in the direction of said path mounted for reciprocal movement on said main frame along said path, said head is mounted on said carriage frame adjacent the downstream end thereof, pallet engaging means is connected to said carriage frame adjacent its upstream end for engaging a pallet and carrying it along said path on movement of the carriage frame along said path, and said second powered means is operatively connected to said carriage for shifting the same along said path.
 4. The apparatus of claim 1, wherein said shifting means comprises a power actuated vertically shiftable member, and which further comprises means mounting said head on said member for limited vertical shifting relative to said member between an extended position at the lower limit of shifting relative to said member and a retracted position shifted upwardly on said member from said extended position, and biasing means operatively interposed between said member and head yieldably urging the head toward its extended position.
 5. The apparatus of claim 4, wherein said shifting means comprises an extensible-contractible ram disposed with its rod directed downwardly, said means mounting the head thereon comprises a connector member secured to said head and mounted on said rod for movement therewith and for vertical sliding movement relative thereto, means limiting shifting of said member between said extended and retracted positions rElative to said shaft, and said biasing means comprises a compression spring interposed between said rod and said head.
 6. The apparatus of claim 4, wherein said control means comprises means operable to sense shifting of said head between its extended and retracted positions and to produce release of said magnetic attachment on shifting of the head to its retracted position.
 7. The apparatus of claim 6, wherein said sensing means comprises a switch element and a switch actuating element, with one of said elements being mounted on said head for movement therewith and the other of said elements being mounted on said vertically shiftable member of said shifting means, with said elements being so positioned that they are spaced from each other when said head is in its extended position, and the switching element and actuating element are in switch operating positions when said head is retracted.
 8. The apparatus of claim 1, which further comprises a main frame, said conveyor includes an elongate substantially horizontal carriage frame mounted for reciprocal movement on the main frame paralleling said path, drive means for producing reciprocal movement of the carriage frame a distance substantially equal to the dimension of a pallet measured in the direction of said path, and means adjacent the upstream end of the carriage for engaging a pallet when the carriage is retracted to an upstream position and for carrying such pallet therewith on movement of the carriage in the downstream direction, and said head is mounted on said carriage and spaced from said pallet engaging means a distance which is substantially equal to a positive odd integer multiplied by one-half of said dimension of a pallet. 